The invention concerns a process for extruding a composite section comprising a beam-like section, in particular a beam-like section made of a light-weight metal, and a facing of at least a part of at least one of the surfaces of the beam-like section in the form of a strip of a different metal, in which process the beam-like section is formed by forcing an unscalped billet through a die and, at the same time, the metal strip passes through the shape giving section of the die. Furthermore, the invention concerns a die for carrying out this kind of extrusion wherein the ratio of the maximum radius of the feed chamber of the die to the minimum radius of the container passage of the die is less than or equal to 0.8.
Heretofore, in order to assure an oxide free surface on the extruded billet and correspondingly a good metal bond, it was necessary to scalp the billet to provide a fresh surface prior to extrusion. The foregoing resulted in decreased productivity and increased operating costs.
In addition, conventional processes use an extrusion die with feed channels at the side through which the metal facing strip is fed to the so called shape-giving or die opening and thereby defined into the direction of extrusion. In practice however the extrusion dies which have been known up to now for this purpose are usually troublesome in production due either to the strip sticking in the die or due to wear caused by the die.
Furthermore, the choice of section shape is often limited to those which are flat on at least a part of the surface.